The present invention relates to a vehicular headlamp having an aiming leveling device, which is mounted on a reflector in the case of a movable-reflector type headlamp or mounted on a lamp body-reflector unit in the case of a movable-unit type headlamp, and which functions as an inclination indicator for detecting and indicating the irradiation angle of the headlamp in the vertical direction.
In a conventional aiming leveling device for a vehicular headlamp as disclosed, for example, in commonly assigned U.S. Pat. No. 5,083,244, as shown in FIGS. 1 to 3, a vehicular headlamp of movable-reflector type includes a reflector 2 on which is mounted a bulb 3. The reflector 2 is tiltably supported on a lamp body 1, which defines a reference member. The tilt angle of the reflector 2 in the vertical direction of the reflector 2 is indicated by an aiming leveling device 4 mounted on the reflector 2.
As shown in FIGS. 2 and 3, the aiming leveling device 4 is constituted by a case 5 having a vessel-like shape opening upward, a linear bubble tube 7, and a cover 6 acting as a bubble tube support frame, suspending and supporting the bubble tube 7. The cover 6 is installed on the case 5 in such a manner that the inclination angle of the cover 6 can be adjusted. Reference numeral 8a represents a zero point adjustment screw; 8b, a compression spring; and 9a and 9b, concave and convex engagement portions between the cover 6 and the case 5.
The cover 6 is held in position by the spring 8b and the screw 8a in such a manner that the angle of inclination of the cover 6 can be adjusted by rotating the screw 8a. Accordingly, it is possible to adjust the position of a bubble in the bubble tube 7, that is, to adjust the zero point of the aiming leveling device.
Reference letter L in FIG. 1 indicates the optical axis of the headlamp. In FIG. 3, reference numeral 2a indicates a plate-like extended portion formed on the reflector 2 for mounting thereon the aiming leveling device, and reference numeral 1a represents an aperture portion provided in the lamp body 1. A transparent cap 1b is attached to this opening portion 1a so that the scale of the aiming leveling device 4 can be read through this transparent cap 1b.
However, the conventional aiming leveling device 4 thus constructed has a complicated structure in that the concave and convex engagement portions 9a and 9b for engaging and holding the case 5 are formed between the cover 6 and the case 5, and the compression spring 8b is required for applying a spring bias to the cover.
An aiming leveling device having a simplified structure is disclosed in commonly assigned U.S. patent application Ser. No. 08/012,777 now U.S. Pat. No. 5,337,222. In the proposed aiming leveling device, as shown in FIG. 4, a bubble tube support frame a is formed by cutting and bending a metal leaf spring body into a predetermined shape. One end a.sub.1 of the support frame a is fixed to a support mount b, with the other end a.sub.2 free to spring upward, while the other end a.sub.2 is received by a head portion c.sub.1 of a zero point adjustment screw c screwed into the support table b in such a manner that a bubble tube d can be held substantially horizontally together with the bubble tube support frame a.
However, even in the proposed aiming leveling device according to U.S. patent application No. 08/012,777 now U.S. Pat. No. 5,337,222 described above, since the spring movement acting on the rear side of the bubble tube support frame a is stopped by the head portion c.sub.1 of the zero point adjustment screw c, a force always acts on the screw engagement portion b.sub.1 of the support table b in the upward direction, that is, in the direction urging the screw to come off.
In addition, an inertial load caused by the up/down motion accompanying the running of a motor vehicle also acts on this screw engagement portion b.sub.1. Since the support table b is made of synthetic resin while the screw c is made of metal, the screw engagement portion b.sub.1 tends wear and be damaged in long-term use. Thus, there is a problem in that the screw engagement portion may over time become unable to properly perform its designated function.